The invention relates generally to coating systems having piston operated fluid supply cylinders, and more particularly to fluid supply cylinders useable for supplying liquid paints to dispensers.
Fluid supply systems that supply fluid from one or more piston operated fluid supply cylinders are known generally and used widely. U.S. Pat. No. 5,632,816 issued May 27, 1997, entitled "Voltage Block" and U.S. Pat. No. 5,725,150 issued on Mar. 10, 1998, entitled "Method and System for an Improved Voltage Block", both assigned commonly herewith and incorporated herein by reference, for example, disclose generally electrostatic coating systems having one or more cylinders with reciprocating pistons for pumping paints to an electrostatic dispenser that sprays atomized and electrically charged paint particles toward a target. A voltage blocking valve directs the supply of paint from a reservoir to the cylinder and to the electrostatic dispenser. The cylinder is generally selectively coupled to one of several different paint reservoirs to permit changing paints supplied therefrom to the electrostatic dispenser. Between paint changes, the cylinder is flushed with solvent to remove any paint and paint residue therefrom and from associated supply conduits.
In known prior art fluid supply cylinders, fluid is drawn into a cylinder chamber through a single fluid port disposed through an end wall of the cylinder while the piston moves away therefrom, and fluid is supplied from the cylinder chamber through the fluid port while the piston moves toward the end wall. In prior art fluid supply cylinders, however, fluid residue has a tendency to accumulate on portions of the cylinder chamber, and particularly on the piston head face opposite the end wall of the cylinder chamber. The accumulation of residue, especially paint residue, can become relatively heavy and difficult to remove, particularly after prolonged operation.
It is known to remove paint residue from fluid supply cylinders by flushing the cylinder chamber with a solvent, for example between paint color changes in the electrostatic systems disclosed in the referenced U.S. Pat. Nos. 5,632,816 and 5,725,150. In prior art cylinders, however, the solvent tends to remove residue accumulated on the central portion of the piston head opposite the fluid inlet port most effectively. Fluid is removed less effectively from other portions of the cylinder chamber including portions of the piston face located radially outwardly of the central portion thereof. To completely remove residue from the cylinder chamber and piston head, at least to an extent necessary to prevent cross contamination of different fluids supplied therefrom, substantial amounts of solvent must be pumped or flushed through the cylinder chamber. But solvent and the disposal thereof is costly, so it is generally desirable to minimize solvent usage. Increased solvent flushing also requires more time, which reduces productivity.
The present invention is drawn generally toward advancements in the art of piston operated fluid supply cylinders, and more particularly to fluid supply cylinders with improved flushability, and useable for supplying fluids in coating systems.
It is an object of the invention to provide novel piston operated fluid supply cylinders that overcome problems with the prior art.
It is also an object of the invention to provide novel piston operated fluid supply cylinders with improved flushability, useable for supplying liquid paints in coating systems, and combinations thereof.
It is another object of the invention to provide novel piston operated fluid supply cylinders that may be flushed relatively quickly and with relatively reduced amounts of solvent, and that are useable for supplying paints in electrostatic coating systems capable of flushing paint residue from the fluid supply cylinder.
It is a more particular object of the invention to provide a fluid supply cylinder comprising generally a piston reciprocatingly disposed in the chamber of a body member, the piston having a head with a face opposite an end wall of the chamber, a plurality of chamber fluid ports disposed in the end wall of the chamber, whereby the reciprocating piston draws fluid into the cylinder and supplies fluid from the chamber through the plurality of chamber fluid ports.
It is another more particular object of the invention to provide novel fluid supply cylinders of the type discussed generally above, further comprising an outer fluid port in the body member, and a plurality of fluid conduits between a corresponding one of the plurality of chamber fluid ports and the outer fluid port. The outer fluid port is preferably located substantially along a central axis of the cylinder chamber, and at least some of the plurality of fluid conduits preferably diverge outwardly from the outer fluid port toward the end wall of the chamber.
These and other objects, aspects, features and advantages of the present invention will become more fully apparent upon careful consideration of the following Detailed Description of the Invention and the accompanying Drawings, which may be disproportionate for ease of understanding, wherein like structure and steps are referenced generally by corresponding numerals and indicators.